1. Field of the Disclosure
The disclosures relates to a device, which enables both the display of information and the input of information. The device combines light emitting elements to provide an information display function and light sensing elements to provide an information-input function. In particular the disclosure relates to a combined information display and information input device based on organic materials wherein an organic light emitting material is used to provide the light emitting function and an organic light sensing material is used to provide the light sensing function. Methods of manufacture of such devices are also the subject of the disclosure.
2. Brief Description of the Prior Art
Apparatus capable of both displaying information and allowing the input of information are known with the most well established technologies operating by means of a touch sensitive panel or film applied over the surface of a standard display such as a backlit LCD or a CRT display. Such displays have the disadvantage that the introduction of a further component beyond those of the display itself adds to the complexity of manufacturing. In addition wear caused to the touch panel by regular contact limits the durability of this component and contact with the surface of the screen may cause distortion of the image displayed.
A number of efforts have been directed at integrating information display and information input functions onto a single substrate and thereby simplifying the manufacture of the displays. To date most of these efforts have been directed at the combination of LCD technology and inorganic semiconductor photosensor technology. The advantage of using photosensors rather than touch sensors is that no contact with the screen Is needed to input information.
The 1990s saw the growth of a display technology based on organic light emitting materials. Light emitting devices based on organic light emitting materials fall into two broad classes, those based on polymeric light emitting materials, as disclosed in WO 90/13148, and those devices based on low molecular weight light emitting materials, so called small molecules, such as disclosed in U.S. Pat. No. 4,530,507. At around the same time it was appreciated that the same semiconductive organic materials which provide the light emitting material in organic light emitting devices could also be used to detect light, see in particular the disclosure of the light sensing properties of light emitting polymers in U.S. Pat. Nos. 5,331,183 and 5,523,555.
It has been proposed to use this dual operating function of light emitting polymers to provide a device capable of both the display and the input of information. U.S. Pat. No. 5,929,845 discloses a scanner based on a matrix of organic light emitting devices with the devices emitting light onto the surface of the image to be scanned, light reflected from this image is detected by the display allowing information about the scanned image to be stored in a suitable information storage means and if desired displayed by means of the matrix of light emitting devices. This scanner device comprises a single matrix of light emitting polymer devices with each device functioning as both a light emitter and a light detector. U.S. Pat. No. 5,504,323 also suggests using a single matrix of organic light emitting devices with each device acting as both light emitter and light detector. GB2315594 discloses a scanning device where organic light emitting devices are used to provide a light source, light from which is reflected from the image to be scanned, this reflected light is detected by light emitting polymer based sensors.
In these prior art displays the organic electronic devices are used to provide both a light emitting function, when forward biased, and a light detecting function, when reverse biased. The disadvantage of such an arrangement is that the organic electronic devices cannot be optimised to perform both functions therefore any improvement in the light sensing property of the device will generally be detrimental to the light emitting property of the device and vice versa. Such devices can then not operate optimally as both right emitting devices and light sensing devices. Further the need to operate the organic electronic devices alternately in two modes requires complex electronic driving circuitry.